gcc6 has fixed a long standing c++ include issue where <cheader>
was different from <header.h> inclusion via

https://gcc.gnu.org/ml/libstdc++/2016-01/msg00025.html

and its also descibed in https://gcc.gnu.org/gcc-6/porting_to.html
rpmio component uses some .cpp and .cc fies which need to use
C stdlib.h from C library and not the C++ libstdc++ header
therefore we pass _GLIBCXX_INCLUDE_NEXT_C_HEADERS so that it
keeps the old behavior

/a/build/tmp/sysroots/raspberrypi2/usr/include/c++/6.0.1/cstdlib:143:11: error: '::getenv' has not been declared
   using ::getenv;
           ^~~~~~
In file included from ../../rpm-5.4.15/system.h:201:0,
                 from ../../rpm-5.4.15/rpmio/rpmjs.cpp:1:
/a/build/tmp/sysroots/raspberrypi2/usr/include/c++/6.0.1/stdlib.h:62:12: error: 'std::getenv' has not been declared
 using std::getenv;

Upstream-Status: Pending
Signed-off-by: Khem Raj <raj.khem@gmail.com>

Index: rpm-5.4.15/rpmio/Makefile.am
===================================================================
--- rpm-5.4.15.orig/rpmio/Makefile.am
+++ rpm-5.4.15/rpmio/Makefile.am
@@ -151,7 +151,7 @@ librpmio_la_SOURCES = \
 	groestl.c hamsi.c jh.c keccak.c lane.c luffa.c md2.c md6.c radiogatun.c\
 	salsa10.c salsa20.c shabal.c shavite3.c simd.c skein.c tib3.c tiger.c \
 	rpmgit.c rpmio-stub.c \
-	rpmjs.cpp rpmjsio.c rpmkeyring.c \
+	rpmjni.cc rpmjs.cpp rpmjsio.c rpmkeyring.c \
 	rpmnix.c rpmodbc.c rpmsql.c set.c \
 	ar.c \
 	argv.c \
@@ -195,7 +195,6 @@ librpmio_la_SOURCES = \
 	rpmhook.c \
 	rpmio.c \
 	rpmiob.c \
-	rpmjni.cc \
 	rpmku.c \
 	rpmlog.c \
 	rpmltc.c \
@@ -279,7 +278,9 @@ keccak.lo: $(top_srcdir)/rpmio/keccak.c
 #rpmjs.lo: $(top_srcdir)/rpmio/rpmjs.c
 #	@$(LTCOMPILE) -O0 -c $<
 rpmjs.lo: $(top_srcdir)/rpmio/rpmjs.cpp
-	@$(LTCOMPILE) -O0 -c $<
+	@$(LTCOMPILE) -O0 -c -D_GLIBCXX_INCLUDE_NEXT_C_HEADERS $<
+rpmjni.lo: $(top_srcdir)/rpmio/rpmjni.cc
+	@$(LTCOMPILE) -O0 -c -D_GLIBCXX_INCLUDE_NEXT_C_HEADERS $<
 
 YACC = byacc -d
 getdate.c: getdate.y